1. Field of the Invention
The present invention relates to a magnetic recording and reproduction apparatus, and in particular, to a magnetic recording and reproduction apparatus in which a sub chassis is movable relative to a main chassis.
2. Description of the Related Art
A magnetic recording and reproduction apparatus for recording information to, and/or reproducing information from a magnetic tape accommodated in a cassette includes two chassis, i.e., a main chassis and a sub chassis.
With reference to FIGS. 10, 11, 12 and 13, a conventional magnetic recording and reproduction apparatus 600 will be described.
In FIG. 10, part (a) is a left side view of a main chassis 400 of the magnetic recording and reproduction apparatus 600, part (b) is a plan view thereof, and part (c) is a right side view thereof.
The main chassis 400 includes a bottom portion 430, a left side section 420a vertical to the bottom section 430, and a right side section 420b vertical to the bottom section 430. The left side section 420a faces the right side section 420b. 
On the bottom section 430 of the main chassis 400, a rotatable head cylinder 412 is provided.
The left side section 420a of the main chassis 400 has a first projection 403 projecting therefrom inward into the main chassis 400, and the right vertical section 420b of the main chassis 400 has a second projection 404 and a third projection 405 both projecting therefrom inward into the main chassis 400.
In FIG. 10, elements other than the rotatable head cylinder 412, the first projection 403, the second projection 404 and the third projection 405 are omitted for the sake of simplicity.
In FIG. 11, part (a) is a left side view of a sub chassis 500 of the magnetic recording and reproduction apparatus 600, part (b) is a plan view thereof, and part (c) is a right side view thereof.
The sub chassis 500 includes a bottom section 531, a left side section 521a vertical to the bottom section 531, and a right vertical section 521b vertical to the bottom section 531. The left side section 521a faces the right vertical section 521b. 
The left side section 521a of the sub chassis 500 has a first guide groove 509 formed therein, and the right vertical section 521b of the sub chassis 500 has a second guide groove 510 and a third guide groove 511 both formed therein.
In FIG. 11 also, elements other than the first guide groove 509, the second guide groove 510, and the third guide groove 511 are omitted for the sake of simplicity.
The magnetic recording and reproduction apparatus 600 (FIGS. 12 and 13) are produced by placing the sub chassis 500 on the main chassis 400.
A cassette (not shown) is mounted on the sub chassis 500 of the magnetic recording and reproduction apparatus 600.
The sub chassis 500 is reciprocally movable relative to the main chassis 400 from a cassette mountable position at which the cassette is mountable on the sub chassis 500 to a tape pull-out position at which a tape in the cassette has been pulled out from a cassette to the rotatable head cylinder 412.
In the magnetic recording and reproduction apparatus 600, the first projection 403 provided on the main chassis 400 is engaged with the first guide groove 509 provided in the sub chassis 500. The second projection 404 provided on the main chassis 400 is engaged with the second guide groove 510 provided in the sub chassis 500. The third projection 405 provided on the main chassis 400 is engaged with the third guide groove 511 provided in the sub chassis 500.
Although omitted in FIGS. 10 and 11, the main chassis 400 and the sub chassis 500 are equipped with a tape pull-out member for pulling out the tape from the cassette and winding the tape around the rotatable head cylinder 412, a tape driving member for driving the tape wound around the rotatable head cylinder 412 and the like.
In FIG. 12, part (a) is a left side view of the conventional magnetic recording and reproduction apparatus 600, and part (b) is a right side view thereof, both at the cassette mountable position.
The sub chassis 500 and the main chassis 400 are engaged with each other. FIG. 12 shows the first projection 403, the second projection 404 and the third projection 405 as components provided on the main chassis 400. The entirety of the main chassis 400 is not shown.
As shown in part (a) of FIG. 12, at the cassette mountable position, the first projection 403 is contactable with the first guide groove 509 at three points a, b and c. The first projection 403 is positioned in both a moving direction represented by arrow A and a vertical direction represented by arrow B.
As shown in part (b) of FIG. 12, the second projection 404 is contactable with the second guide groove 510 at three points a′, b′ and c′. The second projection 404 is positioned in both the moving direction represented by arrow A and a vertical direction represented by arrow B.
As shown in part (b) of FIG. 12, the third projection 405 is contactable with the third guide groove 511 at two points d and e. The third projection 405 is positioned in the vertical direction represented by arrow B.
At the cassette mountable position, the tilt precision of the sub chassis 500 with respect to the main chassis 400 and the positional precision of the sub chassis 500 in the moving direction of arrow A with respect to the main chassis 400 are determined by the engagement of the first projection 403 and the first guide groove 509, the engagement of the second projection 404 and the second guide groove 510, and the engagement of the third projection 405 and the third guide groove 511.
In FIG. 13, part (a) is a left side view of the conventional magnetic recording and reproduction apparatus 600, and part (b) is a right side view thereof, both at the tape pull-out position.
The sub chassis 500 and the main chassis 400 are engaged with each other. FIG. 13 shows the first projection 403, the second projection 404 and the third projection 405 as components provided on the main chassis 400. The entirety of the main chassis 400 is not shown.
As shown in part (a) of FIG. 13, at the tape pull-out position, the first projection 403 is contactable with the first guide groove 509 at three points a, b and c. The first projection 403 is positioned in both the moving direction represented by arrow A and the vertical direction represented by arrow B.
As shown in part (b) of FIG. 13, the second projection 404 is contactable with the second guide groove 510 at three points a′, b′ and c′. The second projection 404 is positioned in both the moving direction represented by arrow A and the vertical direction represented by arrow B.
As shown in part (b) of FIG. 13, the third projection 405 is contactable with the second guide groove 511 at two points d and e. The second projection 405 is positioned in the vertical direction of arrow B.
At the tape pull-out position also, the tilt precision of the sub chassis 500 with respect to the main chassis 400 and the positional precision of the sub chassis 500 in the moving direction of arrow A with respect to the main chassis 400 are determined by the engagement of the first projection 403 and the first guide groove 509, the engagement of the second projection 404 and the second guide groove 510, and the engagement of the third projection 405 and the third guide groove 511.
The above-described conventional magnetic recording and reproduction apparatus 600 have the following problems.
In order to allow the first projection 403 to move along the first guide groove 509, the width of the first guide groove 509 in the vertical direction needs to be slightly larger than the outer diameter of the first projection 403 in the vertical direction. Due to that size difference, the position of the first projection 403 in the vertical direction is not accurately determined with respect to the first guide groove 509.
Similarly, in order to allow the second projection 404 to move along the second guide groove 510, the width of the second guide groove 510 in the vertical direction needs to be slightly larger than the outer diameter of the second projection 404 in the vertical direction. Due to that size difference, the position of the second projection 404 in the vertical direction is not accurately determined with respect to the second guide groove 510.
In general, a plurality of tape guide members for guiding the tape are provided on the sub chassis 500. The tilt and position of these tape guide members need to be positioned with high precision with respect to the rotatable head cylinder 412 provided on the main chassis 400, at the tape pull-out position. Unless the position of the first projection 403 and the second projection 404 in the vertical direction is accurately determined, the angle and position of the sub chassis 500 with respect to the main chassis 400 cannot be determined. In consequence, the tilt and position of the tape guide members cannot be determined with high precision.
The position of the sub chassis 500 in the width direction (i.e., the direction from the left side section 521a and the right vertical section 521b or vice versa) is determined by the left side section 420a and the right vertical section 420b of the main chassis 400 and the left side section 521a and the right vertical section 521b of the sub chassis 500. Therefore, the position of the sub chassis 500 in the width direction cannot be determined with high precision.